1. Field of the Invention
This invention relates to a drain plug, and more particularly to a drain plug which is adapted for use as a draining device for removing fluid from a tank. The invention also relates to a method for removing fluid from a tank which uses the drain plug.
b 2. Description of the Related Art
Drain plugs are used in conjunction with a number of different types of fluid holding receptacles, such as engine crankcases, in order to provide a convenient method for removing the fluid contained in the holding receptacle, when required. Conventional drain plugs are typically bolts having a threaded shaft portion and a head portion, which are screwed into a threaded opening in a wall of the fluid holding receptacle. The bolt is tightened via the head until a washer is clamped between the head portion and the wall of the tank, thereby sealing the threaded opening in the tank. When the fluid in the tank needs to be removed, the plug is unscrewed so that the fluid runs from the tank due to gravity.
However, a major disadvantage of the above-described conventional plugs is that as the plug is unscrewed, the fluid typically rushes out of the tank and onto the tool which is being used for unscrewing the bolt, as well as onto the tool operator's hands. This not only results in a great deal of fluid spillage, but can also burn the operator if the fluid being removed is hot, which is often the case.
Furthermore, since the drain plug itself often becomes slippery and hot due to the exiting fluid, the drain plug is often dropped, whereby it is lost or damaged.
Finally, since the drain plug must be screwed and unscrewed each time the fluid is removed, there is an increased chance that cross-threading can take place, which can lead to the destruction of the drain plug threads and the corresponding drain hole threads.
A number of drain plugs have been designed to overcome some the above-mentioned problems. However, many of these conventional plugs have different physical outer dimensions as compared to the original drain plug which they are designed to replace. The increased physical dimensions precludes the use of these plugs in specific close quarter applications.
U.S. Pat. No. 4,951,723 discloses a drain plug consisting of a head, a body, and a bore extending completely through the head and into the body. A spring and a plunger are disposed within the bore such that the spring biases the plunger past ports or openings in the body which are designed to allow fluid from a tank to pass therethrough. However, in order to prevent the fluid from running out of the tank between the plunger and the inner walls of the bore, O-ring seals are provided in the head, thereby containing the fluid between the inner walls of the bore and the plunger. When fluid is to be removed from the tank, a separate plug is forcibly inserted into the bore via the head portion of the drain plug such that it pushes the plunger against the force of the spring. The plunger is moved against the spring force until the ports or openings are no longer covered by the plunger. Fluid from the tank then enters through the ports and flows out of the tank via a central bore in the separate plug while the O-rings prevent fluid from escaping between the inner wall of the bore and the outer wall of the separate plug.
A major disadvantage of U.S. Pat. No. 4,951,723 resides in the fact that the O-ring seals are subject to cracking and erosion due to the constant abrasion between the O-ring seals and the separate plug and the plunger. Thus, replacement of the drain plug is ultimately required.